The reason her being in skyward sword brought about renewed interest was because how great her design was. Her design makes it possible for her to be a sheik clone/alt, which hasn't been possible since her (ugly) Ocarina of Time model. If it weren't for skyward sword's model, no, I wouldn't want her in smash.
If she were ONLY in skyward sword, I wouldn't want her in smash.
It's the combination of the two. Impa is a long running character AND her Skyward sword model makes her a good fit for smash to replace or be a clone/alt of sheik, who has only been in ONE zelda game, but 3 smash bros games.
I'm more of a diehard Zelda fan than I am smash, so Zelda representation in smash is more important to me than 'smash tradition.' It's why I don't mind sheik being replaced and why I want Ganondorf to receive a complete overhaul and lose his entire moveset. I don't care that his moveset would be cut. Characters get cut all the time. Consider it a cut and then ganondorf is replaced with a newcomer, a 'true' ganondorf.